Three dimensional nanoporous membrane having multiple independent, continuous pore systems

Abstract

According to one embodiment, a composition of matter includes: a first system of continuous voids arranged in a three-dimensional matrix; a second system of continuous voids arranged in the three-dimensional matrix; and a nanoporous barrier separating the first system of continuous voids and the second system of continuous voids. The first system of continuous voids and the second system of continuous voids are interwoven but independent so as to form a plurality of channels through the three-dimensional matrix. Corresponding methods for forming the composition of matter are also disclosed.

What is claimed is: 
     
       1. A composition of matter, comprising:
 a first system of continuous voids arranged in a three-dimensional matrix; 
 a second system of continuous voids arranged in the three-dimensional matrix; and 
 a nanoporous barrier separating the first system of continuous voids and the second system of continuous voids; and 
 wherein the first system of continuous voids and the second system of continuous voids are interwoven but independent so as to form a plurality of channels through the three-dimensional matrix. 
 
     
     
       2. The composition of matter as recited in  claim 1 , wherein the nanoporous barrier comprises a material selected from zinc oxide, alumina, titania, and silica. 
     
     
       3. The composition of matter as recited in  claim 1 , wherein the nanoporous barrier comprises a plurality of pores each having a diameter in a range from about 0.3 nm to about 10 nm. 
     
     
       4. The composition of matter as recited in  claim 1 , wherein the nanoporous barrier is characterized by a maximum thickness in a range from about 0.5 nm to about 10 nm throughout the three-dimensional matrix. 
     
     
       5. The composition of matter as recited in  claim 1 , wherein the second system of continuous voids are characterized by a diameter in a range from about 50 nm to about 1500 nm throughout the three-dimensional matrix. 
     
     
       6. The composition of matter as recited in  claim 1 , wherein the three dimensional matrix is characterized by a length or a diameter in a range from about 800 μm to about 5 mm and a thickness in a range from about 1 μm and about 300 μm. 
     
     
       7. The composition of matter as recited in  claim 1 , comprising a sealant disposed within the first system of continuous voids near a first end of the three-dimensional matrix, wherein the sealant effectively prevents mass transport via the first system of voids through the first end of the three-dimensional matrix. 
     
     
       8. The composition of matter as recited in  claim 7 , wherein the nanoporous barrier comprises titania; and
 wherein the sealant comprises alumina. 
 
     
     
       9. The composition of matter as recited in  claim 1 , comprising one or more chemical species functionalized on one or both sides of the nanoporous barrier. 
     
     
       10. The composition of matter as recited in  claim 9 , the chemical species being selected from a group consisting of carboxyl, hydroxyl, ammonia and amine. 
     
     
       11. The composition of matter as recited in  claim 1 , wherein the nanoporous barrier is characterized by a gradient in nanopore diameter along a first axis of the three-dimensional matrix. 
     
     
       12. The composition of matter as recited in  claim 1 , wherein an average size of the voids of the first system of voids are larger than an average size of the voids of the second system of voids. 
     
     
       13. The composition of matter as recited in  claim 3 , wherein an average size of the voids of the first system of voids are larger than an average size of the voids of the second system of voids. 
     
     
       14. The composition of matter as recited in  claim 1 , wherein the nanoporous barrier is a nanoporous layer forming a porous shell around the second system of continuous voids. 
     
     
       15. The composition of matter as recited in  claim 3 , wherein the second system of continuous voids are characterized by a diameter in a range from about 50 nm to about 1500 nm throughout the three-dimensional matrix. 
     
     
       16. The composition of matter as recited in  claim 7 , wherein the sealant effectively allows mass transport via the second system of voids through the first end of the three-dimensional matrix. 
     
     
       17. The composition of matter as recited in  claim 1 , wherein the nanoporous barrier defines a plurality of interfaces between the first system of continuous voids and the second system of continuous voids. 
     
     
       18. The composition of matter as recited in  claim 1 , comprising a sealant sealing the first system of continuous voids and the second system of continuous voids along a first end of the three-dimensional matrix, wherein the sealant comprises a second material and the sealant is defined by:
 a first region comprising ligaments interspersed with voids of the first system of continuous voids and/or the second system of continuous voids, wherein the voids in the first region do not include any of the second material; 
 a second region comprising ligaments interspersed with voids of the first system of continuous voids and/or the second system of continuous voids, wherein the voids in the second region are partially filled with the second material; and 
 a third region comprising ligaments having former voids of the first system of continuous voids and/or the second system of continuous voids, wherein the former voids in the third region are filled with the second material. 
 
     
     
       19. A method for forming the composition of matter of  claim 1 , the method comprising:
 dealloying an alloy to form a matrix of ligaments interspersed with a first system of continuous voids; 
 sealing at least one end of the matrix; 
 forming a conformal layer of a material on surfaces of the ligaments exposed to the first system of continuous voids; and 
 unsealing the matrix to form the three-dimensional matrix having at least two continuous, independent pore systems. 
 
     
     
       20. The method as recited in  claim 19 , the alloy comprising a gold/silver alloy, and the dealloying comprising removing substantially all silver from the alloy by etching with an aqueous nitric acid solution to form the matrix of ligaments.